ideal placement of beds N-S or E-W

Its a simple question which I have been meaning to look up in some of my garden books.  A quick google search doesn't decisively settle it for me.  given I am aiming for polyculture what do you think the best way to go is:  rows going E to W or N to S?

am i right in thinking E to W would warm the soil the quickest in the spring and keep it warm at night?

N to S seems to allow for more vertical space w/ taller plants towards the back of the plot.

anyway I can see merits in both.  currently my beds are N to S & i am debating changing them...

I have seen valid arguments for each option.  Some factors need to be considered, including shape of property, slopes, and surrounding shade factors.  For example, I am looking at a property that is approx 1200 feet (N/S) x 400 feet (E/W).  It currently has a stripe approx 130' x 1000 (3A) running down the middle of it (N/S) that has been cleared.  The W half of the stripe is level. while the E side is at a fair slope.  On either side of the clearing, there are dense plantings of (mostly hardwood) trees.  With that layout, I feel that NS orientation would give me maximum sun (especially on the sloped area which will be mostly shaded in the afternoon).  Considering my 3A clearing, I will have a lot of "edge" area to deal with.  If the same property was rotated 90°, I would probably be thinking E/W orientation.

In the Southern hemisphere,  a N->S orientation is the standard recommendation to give each individual plant the most sun possible.
That's assuming they're planted short front, tall back.
But in the end, a lot depends on your  geography.
The most important factors for me is getting the most sunlight and avoiding plants shading each other out, so N->S, short->tall.

it would all depend on your climate and what you are growing, however, I don't do rows in my polyculture, I use beds..

I also use a combo of full size trees, semi dwarf, dwarf and super dwarfs, some shrubs and some vines..some trellises..etc.

I try to keep the taller trees on the North (sun is south here) side of the garden with the shorter trees going more and more to the south, including shrubs and cane fruits ..

I try to keep "some" sun on everything that likes sun, although some shade part day will hit areas of the garden through out the day.

I also try to think about wind, not just sun, as we have strong NW'ly winds here..so we are putting in windbreaks on the east and then putting hedgrows around the garden to block even more wind.

I have a hedgerow on the north side of the food forest garden of wild plums, mulberries, and hazelnuts and they are going to be protected from a jerusalem artichoke hedge to the north of that when I get those moved, and there is a forest north of that..

my Western side is a mix of berry bushes and cane fruits..I will have a dozen different raspberry species and 2 kinds of blackberies and a large fruited hawthorne and a buffalo berry (found out I need to find out if it is male or female and get another one of those someday)...didn't know.

My southern hedgerow is june and service berry and several species of blueberries with a creeping wintergreen..

in beds in the garden itself ar mixes of fruit trees and shrubs as well as perennial gerbaceous plants and herbs and some annuals in the summer and vines..I have 3 apples, one sweet 16, one braeburn, and one snow in this garden, 2 north star cherries and 2 bush cherries coming, some paw paw,a mountain ash, 3 dwarf pears, a baby goumi, grapes, coming some honeyberry and kiwi  climbing roses and some mixed flowers too for pollination, asparagus on the east and some rhubarb, horseradish, etc..

the beds are circular and a few that are rctangular that are raised and edged..some of the beds are hugel based.

I have heard roots grow north south, so best to grow beds east west.
Next guy might argue you are walking on your roots then.
You crowd the roots or you walk on them.

quick search on roots / magnetism found
http://www.buzzle.com/articles/the-effect-of-magnetism-on-plant-growth.html